Ovulation & Fertile Window Calculator

Estimate your ovulation date and fertile window based on your menstrual cycle. Enter the first day of your last period and your cycle information to get an estimated fertile period.

Note: Calculations are estimates.

First Day of Your Last Period *

Select the first day of your most recent menstrual period.

Your Average Cycle Length (days) *

Recommended range: 21–35 days. (Example: 28 days)

Need Personalized Fertility Guidance?

Every person's fertility journey is different. If you have irregular periods, difficulty conceiving, or questions about ovulation and fertility, our fertility specialists can help you understand your options.

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Your Estimated Results

Estimated Ovulation Date

Estimated Fertile Window

Start Date -

End Date -

Menstrual Cycle Timeline

The timeline below shows the estimated cycle days and corresponding calendar dates starting from your period start date (Day 1):

Period (Days 1-5)

Fertile Window

Ovulation Day

Normal Day

Important: This calculator provides an estimate based on menstrual cycle information and should not be considered a medical diagnosis. Ovulation can vary from cycle to cycle, especially when periods are irregular. For personalized fertility advice, consult a qualified fertility specialist.